For antenna current measurements i'm using a simple full wave rectifier
out of 1N4148 diodes (UF5404 alternatively, for example), a ferrite core
with a high mu and about 40 turns secondary (1 turn primary) , as well
as 100nF, a R network to drive an analog meter (100uA or 1mA) for the
desired range. I find this extremely simple, cheap, nearly lossless and
quite accurate. I do not at all understand why antenna current
measurements (in the kHz range) appears to be problematic for some.
Does it matter if the device costs 1E-24 or 0.001 or 0.1 or 1 or 5
amounts of your preferred currency? :-)
73, Stefan
Am 15.12.2014 12:54, schrieb M0FMT:
Hi all
A 60p festoon auto bulb from Halfords in series with the ant up lead serves
equally well. There is generally no need for antenna current precision
measurement its really tune for max smoke i.e. max brightness. A reasonably
accurate self calibrating indication of current in the up lead subjectively
judging the brightness relative to the DC current rating of the bulb. A more
sophisticated set up can be achieved at extra expense.
73 es GL Pete M0FMT IO91UX
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appreciated.
--- On Sun, 14/12/14, Alan Melia<[email protected]> wrote:
From: Alan Melia<[email protected]>
Subject: LF: Antenna Current meters
To: [email protected], [email protected]
Date: Sunday, 14 December, 2014, 16:31
Hi all there has been discussion
about Aerial Current measurement on many
occassions in the past, and many have built versions of the
"Clothes Peg"
clip on ammeter.
Dave Powis G4HUP announced a kit for an HF clip-on current
meter in the
December Radcom. After some prodding by me he has had a
sample tested at 136
and 475kHz and as expected the instuments works well and
sensitivity is flat
from here up to 30MHz or more. The instructions include a
simple calibration
proceedure. Sensitivity down to 100mA FSD allows it to be
used with low
power systems where the use of a thermocouple RF meter is
not posssible.
Dave also produces a board intended to break out the IF
signal from many
standard tranceivers for input to an SDR dongle. These were
intended to work
in the IF frequency range and use SMD parts to give an
add-in pcb little
larger than a postage stamp. A look at the circuit shows
that this is very
similar to the circuit used by Roelof (mini-whip) and others
for use in
E-field antennas. I believe the coupling capacitors will
need to be
increased in size, but I believe Dave can produce these for
LF to order,
either as a kit or completed board. He has not yet had a
chance to try this
out at LF but it's a chance to experiment at little cost.
Getting the
receive antenna away from habitation and power wiring
is a good move at VLF
!.
I have no pecunary interest but I admit that Dave is a good
friend and ex
work collegue, and an excellent engineer. Look at his
web pages
http://g4hup.com
email [email protected]
Alan
G3NYK
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